One-component, waterborne film-forming composition

ABSTRACT

A film-forming composition that includes a stable aqueous dispersion of a mixture of a polyester polyol and a carboxylic acid-containing acrylic polymer polyol and a crosslinking agent having functional groups reactive with hydroxyl groups. The weight ratio of polyester polyol to acrylic polymer polyol is in the range of 10:90 to 30:70. The crosslinking agent is one or more blocked isocyanates or aminoplasts. The equivalent ratio of hydroxyl groups to reactive functional groups on the crosslinking agent is from 0.8:1 to 1.7:1. The film forming composition can be used in multi-layer composite coating compositions that include a base coat layer and a substantially pigment-free topcoat deposited over at least a portion of the base coat layer, the topcoat composition including the present film-forming composition.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to aqueous coating compositions aswell as multi-component composite coating compositions includingpigmented or colored base coats overcoated with transparent or cleartopcoats, providing good smoothness and appearance in automotive coatingapplications while having a low volatile organic compound content.

[0003] 2. Background of the Invention

[0004] Over the past decade, there has been a concerted effort to reduceatmospheric pollution caused by volatile solvents that are emittedduring the painting process. However, it is often difficult to achievehigh quality, smooth coating finishes, such as are required in theautomotive industry, without using organic solvents which contributegreatly to flow and leveling of a coating.

[0005] One of the major goals of the coatings industry is to minimizethe use of organic solvents by formulating waterbome coatingcompositions which provide a smooth, high gloss appearance, as well asgood physical properties including resistance to acid rain.Unfortunately, many waterbome coating compositions do not provideacceptable appearance. Many automotive manufacturers are interested incoatings that contain low amounts of volatile organic compounds (VOCs).

[0006] Another challenge to formulators of waterborne coatings is toprovide good acid resistance while maintaining acceptable physicalproperties. Lack of humidity resistance or blushing is another problemfacing waterborne coating formulators.

[0007] U.S. Pat. No. 4,350,809 to Fischer et al. discloses a process forthe preparation of copolymers containing hydroxyl groups by free radicalpolymerization of at least two unsaturated copolymerizable monomers, atleast one of which contains at least one carboxyl group, in the presenceof at least one alkyl glycidyl ester of an aliphatic saturatedmonocarboxylic acid with a tertiary or quaternary α-carbon atom. Theresulting polymers are advantageous because of their relatively lowsolution viscosities.

[0008] U.S. Pat. No. 5,663,265 to Epple et al. discloses low-viscositycopolymers useful in coating compositions. The copolymers containhydroxyl and carboxyl groups and are obtained by free-radicalpolymerization of at least two olefinically unsaturated copolymerizablemonomers of which at least one contains at least one carboxyl group andat least one is sterically hindered in the presence of one or moreglycidyl esters of aliphatic saturated monocarboxylic acids having atertiary or quaternary α-carbon atom. The copolymers are useful inclearcoat coating compositions, which demonstrate notable resistance tosulfuric acid and xylene, as well as a high degree of hardness.

[0009] U.S. Pat. No. 5,596,057 to Epple et al. discloses low viscositycopolymers prepared by bulk polymerization. The polymerization includescharging a material with functional groups that react with the carboxylgroups of the monomers and polymerizing at least two olefinicallyunsaturated copolymerizable monomers, at least one of which contains atleast one carboxyl group and at least one of which issterically-hindered. The copolymers are useful in coating compositions.

[0010] U.S. Pat. No. 4,322,508 to Peng et al. discloses a thermosettingcoating composition which includes a hydroxy functional component and acrosslinking agent capable of reacting with hydroxy functionality of thehydroxy functional component. The hydroxy functional component includesan oligoester formed by an esterification reaction between a carboxylicacid and an epoxide and a hydroxy functional copolymer. The hydroxyfunctional copolymer includes residues from one or more hydroxyfunctional monomers. The thermosetting compositions have a short shelflife, however, because the oligoester and hydroxy functional copolymerin the hydroxy functional component tend to separate over time.

[0011] It would be desirable to provide a coating composition whichprovides the benefits of including a combination of hydroxy functionalpolyesters and hydroxy functional acrylic copolymers, such that they donot tend to separate over time, providing a storage stable coatingcomposition. The resultant coatings should have a balance of physicalproperties, including high gloss, hardness, impact resistance,flexibility, weatherability and chemical resistance.

SUMMARY OF THE INVENTION

[0012] The present invention is directed to a one-component, waterbomefilm-forming composition comprising:

[0013] (A) a stable aqueous dispersion of a mixture of a polyesterpolyol and a carboxylic acid-containing acrylic polymer polyol, whereinthe weight ratio of polyester polyol to acrylic polymer polyol is in therange of 10:90 to 30:70; and

[0014] (B) a crosslinking agent having functional groups reactive withthe hydroxyl groups in (A) selected from the group of blockedisocyanates and aminoplasts; wherein the equivalent ratio of hydroxylgroups in (A) to reactive functional groups in (B) is from 0.8:1 to1.7:1.

[0015] The present invention is further directed to a multi-layercomposite coating that includes:

[0016] (I) a base coat layer deposited from a pigmented film-formingbase coat composition; and

[0017] (II) a substantially pigment free topcoat deposited over at leasta portion of the base coat layer (I) from a topcoat composition thatincludes the one-component, waterbome film-forming composition describedabove.

[0018] The present invention is also directed to a coated substrate. Thecoated substrate includes a substrate and the one-component, waterbomefilm-forming composition described above over at least a portion of thesubstrate.

[0019] The present invention is additionally directed to a coatedsubstrate that includes a substrate and the multi-layer compositecoating composition described above over at least a portion of thesubstrate.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Other than in the operating examples, or where otherwiseindicated, all numbers expressing quantities of ingredients, reactionconditions and so forth used in the specification and claims are to beunderstood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the present invention. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

[0021] Notwithstanding that the numerical ranges and parameters settingforth the broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical values, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

[0022] Also, it should be understood that any numerical range recitedherein is intended to include all sub-ranges subsumed therein. Forexample, a range of “1 to 10” is intended to include all sub-rangesbetween and including the recited minimum value of 1 and the recitedmaximum value of 10, that is, having a minimum value equal to or greaterthan 1 and a maximum value of equal to or less than 10. Because thedisclosed numerical ranges are continuous, they include every valuebetween the minimum and maximum values. Unless expressly indicatedotherwise, the various numerical ranges specified in this applicationare approximations.

[0023] As used herein, the term “substantially free” is meant toindicate that a material is present as an incidental impurity. In otherwords, the material is not intentionally added to an indicatedcomposition, but may be present at minor or inconsequential levelsbecause it was carried over as an impurity as part of an intendedcomposition component.

[0024] As used herein, by “thermosetting composition” is meant one which“sets” irreversibly upon curing or crosslinking, wherein the polymerchains of the polymeric components are joined together by covalentbonds. This property is usually associated with a cross-linking reactionof the composition constituents often induced by heat or radiation.Hawley, Gessner G., The Condensed Chemical Dictionary Ninth Edition,page 856; Surface Coatings, vol. 2, Oil and Colour Chemists'Association, Australia, TAFE Educational Books (1974). Once cured orcrosslinked, a thermosetting composition will not melt upon theapplication of heat and is insoluble in solvents. By contrast, a“thermoplastic composition” comprises polymeric components which are notjoined by covalent bonds and thereby can undergo liquid flow uponheating and are soluble in solvents. Saunders, K. J., Organic PolymerChemistry, pp. 41-42, Chapman and Hall, London (1973).

[0025] As used herein, “polymer” is meant to encompass oligomer, andincludes without limitation both homopolymers and copolymers. Also, asused herein, “reactive” refers to a functional group that forms acovalent bond with another functional group under conditions sufficientto cure the composition. As used herein, “(meth)acrylate” and like termsare intended to include both acrylates and methacrylates.

[0026] As used herein, “substantially pigment-free coating composition”means a coating composition which forms a transparent coating, such as aclearcoat in a multi-component composite coating composition. Suchcompositions are sufficiently free of pigment or particles such that theoptical properties of the resultant coatings are not seriouslycompromised. As used herein, “transparent” means that the cured coatinghas a BYK Haze index of less than 50 as measured using a BYK/Haze Glossinstrument.

[0027] As used herein, the phrase components “are different from eachother” refers to components which do not have the same chemicalstructure as other components in the composition.

[0028] As used herein, “cure” as used in connection with a composition,e.g., “composition when cured,” means that any crosslinkable componentsof the composition are at least partially crosslinked. In certainembodiments of the present invention, the crosslink density of thecrosslinkable components, i.e., the degree of crosslinking, ranges from5% to 100% of complete crosslinking.

[0029] As used herein, “stable dispersion” refers to a liquid having aliquid continuous phase and a dispersed phase, which may be a liquid, asolid or a combination thereof, where the dispersed phase does notagglomerate, coalesce, settle or separate from the continuous phasebetween the period of time the dispersion is prepared and when it isused, typically a period of time not exceeding two years at ambientconditions.

[0030] The multi-component composite coating of the present invention isuseful in a variety of coating applications, and is particularly usefulin automotive coating applications. The multi-component compositecoating composition comprises a base coat layer and a transparent orclear topcoat layer formed from an aqueous topcoat coating compositionwhich is applied over the base coat.

[0031] The present one-component, waterbome film-forming compositionincludes:

[0032] (A) a stable aqueous dispersion of a combination of a polyesterpolyol and a carboxylic acid-containing acrylic polymer polyol; and

[0033] (B) a crosslinking agent having functional groups that arereactive with the hydroxyl groups in (A). The crosslinking agents aretypically blocked polyisocyanates and/or aminoplasts. The film-formingcompositions of the present invention typically are “thermosettingcompositions” as defined above.

[0034] The polyester polyol component in (A) provides flow and levelingproperties to the waterbome film-forming composition. These physicalproperties of the composition lead to a smooth topcoat film in themulti-component composite coating. The polyester polyol is present in anamount sufficient to provide a smooth film as indicated by theoccurrence of no more than three craters in an 4 inch (10.2 cm) by 10inch (25.4 cm) coated area.

[0035] The acrylic polymer polyol component in (A) provides filmproperties such as hardness, gloss, acid resistance and delaminationresistance in the topcoat film in the multi-component composite coatingcomposition. The acrylic polymer polyol is present in an amountsufficient to provide a 20° gloss as measured using a Novo GlossStatistical Glossmeter (Paul N. Gardner Company, Inc., Pompano Beach,Fla.) of at least 90, typically at least 95 of the multi-componentcomposite coating composition.

[0036] The weight ratio of the polyester polyol to the acrylic polymerpolyol in (A) may be 10:90 or higher, in some cases 12.5:87.5 or higher,in other cases 15:85 or higher and at other times 17.5:82.5 or higher.Additionally, the weight ratio of the polyester polyol to the acrylicpolymer polyol in (A) may be 30:70 or lower, in some cases 27.5:72.5 orlower, in other cases 25:75 or lower and at other times 22.5 to 77.5.The weight ratio of the polyester polyol to the acrylic polymer polyolin (A) may be 20:80. The higher and lower designation refers to thelevel of the polyester polyol. The weight ratio of the polyester polyolto the acrylic polymer polyol is determined by the properties that areto be incorporated into the resulting coating. The weight ratio of thepolyester polyol to the acrylic polymer polyol may be any value or anyrange of values inclusive of those stated above.

[0037] When the crosslinking agent of (B) comprises a blockedpolyisocyanate, the equivalent ratio of hydroxyl groups in (A) toisocyanate groups in (B) maybe 0.8:1 or higher, in some cases 1:1 orhigher, in other cases 1.1:1 or higher, in some instances 1.2:1 orhigher and at other times 1.35:1 or higher. Additionally, the equivalentratio of hydroxyl groups in (A) to isocyanate groups in (B) may be 1.7:1or lower, in some cases 1.65:1 or lower, in other cases 1.6:1 or lower,in some instances 1.55:1 or lower and at other times 1.5:1 or lower. Theequivalent ratio of hydroxyl groups in (A) to isocyanate groups in (B)may be 1.4:1. The higher and lower designation refers to the level ofthe hydroxyl groups. The equivalent ratio of hydroxyl groups in (A) toisocyanate groups in (B) is determined by the properties that are to beincorporated into the resulting coating. When the amount of isocyanatefunctionality in (B) is too high, the composition may react and/or maybe unstable. When the hydroxyl functionality is too high, an undesirablesoft film coating may result. The equivalent ratio of hydroxyl groups in(A) to isocyanate groups in (B) may be any value or any range of valuesinclusive of those stated above.

[0038] As used herein, “equivalent ratio” means the ratio of chemicalequivalents of hydroxyl functionality to chemical equivalents offunctional groups that are reactive with hydroxyl groups. A chemicalequivalent is the quantity of a material that supplies one mole of afunctional group. T. L. Brown and H. E. LeMay, Chemistry: The CentralScience, page 346, 1977.

[0039] When the crosslinking agent of (B) is an aminoplast, it can bepresent in the film-forming composition in an amount of at least 5percent by weight, in some cases at least 10 percent by weight, in othercases at least 15 percent by weight, in some instances at least 20percent by weight and at other times 20 percent by weight based on thetotal resin solids in the film-forming composition. Additionally, theamount of the aminoplast crosslinking agent (B) may be up to 60 percentby weight, in some cases up to 55 percent by weight, in other cases upto 50 percent by weight, in some instances up to 40 percent by weightand at other times up to 30 percent by weight based on the total resinsolids in the film-forming composition. The amount of aminoplastcrosslinking agent (B) is determined by the properties that are to beincorporated into the resulting coating. When the amount of aminoplastis too high, the composition may react and/or may be unstable. When theamount of aminoplast is too low, an undesirable soft film coating mayresult. The amount of aminoplast crosslinking agent (B) present in thefilm-forming composition may be any value or any range of valuesinclusive of those stated above.

[0040] In an embodiment of the present invention, component (A) may beprepared by polymerizing a mixture of ethylenically unsaturatedpolymerizable monomers in the presence of at least one glycidyl ester ofan aliphatic saturated monocarboxylic acid and at least one polyesterpolyol. In this embodiment, the monomer mixture includes at least onecarboxylic acid group-containing monomer and at least one primaryhydroxyl group-containing monomer, which form an acrylic polyol. Theglycidyl ester of an aliphatic saturated monocarboxylic acid acts as asolvent for the reactants.

[0041] Typically, when the polymerization is complete, an amine is addedto component (A) in an amount sufficient to provide a pH of from 7 to 10when component (A) is dispersed in water. In an embodiment of thepresent invention, the pH is increased by using one or more suitablevolatile amines. Examples of suitable volatile amines include, but arenot limited to, dimethylethanolamine, ammonia, triethyl amine anddiethyl propanol amine.

[0042] The polymerization described above is generally carried out byintroducing the monomer mixture that includes at least one carboxylicacid group-containing monomer and at least one primary hydroxylgroup-containing monomer to a suitable reactor to which at least oneglycidyl ester of an aliphatic saturated monocarboxylic acid and atleast one polyester polyol are added. A suitable free radicalpolymerization initiator is also added. In an embodiment of the presentinvention, the polymerization is run in the substantial absence of asolvent.

[0043] Any suitable free radical initiator may be used in thepolymerization. Suitable free radical initiators include, but are notlimited to, thermal initiators, photoinitiators and oxidation-reductioninitiators. Examples of thermal initiators include, but are not limitedto, azo compounds, peroxides and persulfates. Suitable persulfatesinclude, but are not limited to, sodium persulfate and ammoniumpersulfate. Oxidation-reduction initiators may include, as non-limitingexamples perulfate-bisulfite systems as well as systems utilizingthermal initiators in combination with appropriate metal ions such asiron or copper.

[0044] Suitable azo compounds include, but are not limited to,non-water-soluble azo compounds such as1-1′-azobis(cyclohexanecarbonitrile), 2-2′-azobisisobutyronitrile,2-2′-azobis(2-methylbutyronitrile), 2-2′-azobis(propionitrile),2-2′-azobis(2,4-dimethylvaleronitrile), 2-2′-azobis(valeronitrile),2-(carbamoylazo)-isobutyronitrile and mixtures thereof, andwater-soluble azo compounds such as azobis tertiary alkyl compoundsinclude, but are not limited to, 4-4′-azobis(4-cyanovaleric acid),2-2′-azobis(2-methylpropionamidine) dihydrochloride,2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],4,4′-azobis(4-cyanopentanoic acid),2,2′-azobis(N,N′-dimethyleneisobutyramidine),2,2′-azobis(2-amidinopropane) dihydrochloride,2,2′-azobis(N,N′-dimethyleneisobutyramidine) dihydrochloride andmixtures thereof.

[0045] Suitable peroxides include, but are not limited to, hydrogenperoxide, methyl ethyl ketone peroxides, benzoyl peroxides, di-t-butylperoxides, di-t-amyl peroxides, dicumyl peroxides, diacyl peroxides,decanoyl peroxide, lauroyl peroxide, peroxydicarbonates, peroxyesters,dialkyl peroxides, hydroperoxides, peroxyketals and mixtures thereof.

[0046] Any suitable carboxylic acid group-containing monomer may be usedto prepare the acrylic polyol used in the compositions of the presentinvention, so long as it can be polymerized under the conditionsdescribed above. Examples of suitable carboxylic acid group-containingmonomers include, but are not limited to, (meth)acrylic acid, maleicacid and its corresponding anhydride, itaconic acid, aconitic acid,fumaric acid, alpha-halo acrylic acid, vinyl acetic acid andbeta-carboxymethyl (meth)acrylate.

[0047] Any suitable monomer containing a primary hydroxyl group may beused to prepare the acrylic polyol used in the compositions of thepresent invention, so long as it can be polymerized under the conditionsdescribed above. Examples of suitable monomers containing a primaryhydroxyl groups include, but are not limited to, hydroxyethylacrylate,hydroxyethylmethacrylate, hydroxypropyl acrylate,hydroxypropylmethacrylate, hydroxybutyl (meth)acrylate, glycerol allylether, ethylene oxide esters of (meth)acrylic acid and propylene oxideesters of (meth)acrylic acid.

[0048] Other suitable polymerizable ethylenically unsaturated monomersmay be used to prepare the acrylic polyol of the present invention.Other suitable monomers include, but are not limited to, C₁-C₃₀aliphatic alkyl esters of (meth)acrylic acid, non-limiting examples ofwhich include methyl(meth)acrylate, ethyl(meth)acrylate,propyl(meth)acrylate, N-butyl(meth)acrylate, t-butyl(meth)acrylate,2-ethylhexyl(meth)acrylate, isobornyl (meth)acrylate, glycidyl(meth)acrylate, dimethylaminoethyl (meth)acrylate, N-butoxy methyl(meth)acrylamide, lauryl (meth)acrylate, cyclohexyl (meth)acrylate and3,3,5-trimethylcyclohexyl (meth)acrylate. Other non-limiting examples ofsuitable monomers include (meth)acrylamide, N,N dialkyl(meth)acrylamides dimethylaminoethyl (meth)acrylate, vinyl aromaticcompounds such as styrene and vinyl toluene, nitriles such as(meth)acrylonitrile, vinyl and vinylidene halides such as vinyl chlorideand vinylidene fluoride and vinyl esters such as vinyl acetate.

[0049] Carbamate functional groups can be included in the acrylic polyolpolymer by copolymerizing the acrylic monomers with a carbamatefunctional vinyl monomer, such as a carbamate functional alkyl ester ofmethacrylic acid, or by reacting a hydroxyl functional acrylic polymerwith a low molecular weight carbamate functional material, such as canbe derived from an alcohol or glycol ether, via a transcarbamoylationreaction. Other useful carbamate functional monomers are disclosed inU.S. Pat. No. 5,098,947 to Metzger et al., which is incorporated hereinby reference.

[0050] While not being bound to a single theory, it is believed thatforming the acrylic polyol in the presence of the polyester polyolresults in the formation of a stable polymer-polymer complex. Thestability of the polymer-polymer complex may arise from the associationof hydrophobic portions of the polyester polyol and acrylic polyolpolymer backbones. On the other hand, a portion of the formed acrylicpolyol may graft onto the polyester polyol backbone. Additionally, theacrylic polyol and polyester polyol may become inseparably commingledand entangled. Combinations of associations may exist to the point thatan interpenetrating polymer network is formed between the polyesterpolyol and acrylic polyol. Regardless of the method or reason, thecombination of the acrylic polyol and polyester polyol demonstratessuperior storage stability when compared to prior art physical blends ormixtures of such materials.

[0051] In order to facilitate the formation of an interpenetratingpolymer network structure, one or more crosslinking monomers may beutilized in the monomer mixture. The amount of crosslinking monomer usedwill depend on the degree of branching or crosslinking desired. If mildbranching is desired, a relatively low level of crosslinking monomerwill be used, whereas if a highly crosslinked acrylic polyol is desireda higher level of crosslinking monomer will be used. Suitablecrosslinking monomers include compounds having two or more functionalgroups that will react with a free radical. As a non-limiting example,compounds having two or more reactive unsaturated groups may be used.Suitable crosslinking monomers that may be used in the monomer mixinclude, but are not limited to, ethylene glycol di(meth)acrylate,triethylene glycol di(meth)acrylate, tetraethylene glycoldi(meth)acrylate, 1,3-butylene glycol di(meth)acrylate,trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate,pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, glycerolallyloxy di(meth)acrylate, 1,1,1-tris(hydroxymethyl)ethanedi(meth)acrylate, 1,1,1-tris(hydroxymethyl)ethane tri(meth)acrylate,1,1,1-tris(hydroxymethyl)propane di(meth)acrylate,1,1,1-tris(hydroxymethyl)propane tri(meth)acrylate, triallyl cyanurate,triallyl isocyanurate, triallyl trimellitate, diallyl phthalate, diallylterephthalate, divinyl benzene, methylol (meth)acrylamide, triallylamineand methylenebis (meth)acrylamide.

[0052] In the polymerization method described above, the equivalentratio of the carboxylic acid groups from the carboxylic acidgroup-containing monomer to the epoxy group of the glycidyl ester of analiphatic saturated monocarboxylic acid may be greater than 1:1, in somecases at least 1.01:1, in other cases at least 1.1:1, in other instances1.2:1 and in other cases at least 1.25:1. In a further embodiment, thecarboxylic acid groups from the carboxylic acid group-containing monomerare present in excess of the epoxy group of the glycidyl ester of analiphatic saturated monocarboxylic acid. Generally, the carboxylic acidfunctional groups of the carboxylic acid functional monomers react withthe epoxy group of the glycidyl ester of an aliphatic saturatedmonocarboxylic acid, resulting in the formation of the correspondingester group and a secondary hydroxyl group.

[0053] Any suitable glycidyl ester of an aliphatic saturatedmonocarboxylic acid may be used. In an embodiment of the presentinvention, the glycidyl ester of an aliphatic saturated monocarboxylicacid is a glycidyl ester having structure (I).

[0054] In structure (I), R¹ is C₁-C₁₈ linear or branched alkyl and R²and R3 are independently selected from H and C₁-C₁₈ linear or branchedalkyl. Non-limiting examples of suitable glycidyl esters of carboxylicacids include VERSATIC ACID 911 and CARDURA E, each of which iscommercially available from Resolution Performance Products.

[0055] The acrylic polyol used in the present invention may be of anysuitable molecular weight. The molecular weight of the acrylic polyolmay be at least 250, in some cases at least 500, in other cases at least750, in some instances at least 1,000 and in other instances at least1,500. Additionally, the molecular weight of the acrylic polyol maybe upto 25,000, in some cases up to 15,000, in other cases up to 10,000, insome instances up to 7,500 and in other instances up to 5,000 asdetermined by GPC using polystyrene standards. The molecular weight ofthe acrylic polyol is selected based on the flow properties desired incomponent A and the properties desired in the coating film resultingfrom the present one-component, waterborne film-forming composition. Themolecular weight of the acrylic polyol may be any value or any range ofvalues inclusive of those stated above.

[0056] As described above, the carboxylic acid functional monomer may bepresent in excess compared to the glycidyl ester of an aliphaticsaturated monocarboxylic acid. Thus, the acrylic polyol may containcarboxylic acid functionality resulting from residual or unreactedcarboxylic acid groups. The acrylic polyol may have an acid value of atleast 1, in some cases at least 2, in other cases at least 5, in someinstances at least 10 and in other instances at least 25 mg KOH/g resin.Additionally, the acrylic polyol may have an acid value of not more than100, in some cases not more than 75, in other cases not more than 50, insome instances not more than 40 and in other instances not more than 35mg KOH/g resin. The acid value (number of milligrams of KOH per gram ofsolid required to neutralize the acid functionality in the resin) is ameasure of the amount of acid functionality in the resin. The acid valueof the acrylic polyol may be any value or any range of values inclusiveof those stated above.

[0057] Any suitable polyester polyol may be used in the presentinvention. As a non-limiting example, useful polyester polymerstypically include the condensation products of polyhydric alcohols andpolycarboxylic acids. Suitable polyhydric alcohols can include ethyleneglycol, neopentyl glycol, trimethylol propane and pentaerythritol.Suitable polycarboxylic acids can include adipic acid, 1,4-cyclohexyldicarboxylic acid and hexahydrophthalic acid. Besides the polycarboxylicacids mentioned above, functional equivalents of the acids such asanhydrides where they exist or lower alkyl esters of the acids such asthe methyl esters can be used. Also, small amounts of monocarboxylicacids such as stearic acid can be used. The ratio of reactants andreaction conditions are selected to result in a polyester polymer withthe desired pendent functionality, i.e., carboxyl or hydroxylfunctionality.

[0058] As a non-limiting example, hydroxyl group-containing polyesterscan be prepared by reacting an anhydride of a dicarboxylic acid such ashexahydrophthalic anhydride with a diol such as neopentyl glycol in a1:2 molar ratio. Where it is desired to enhance air-drying, suitabledrying oil fatty acids may be used and include those derived fromlinseed oil, soya bean oil, tall oil, dehydrated castor oil or tung oil.

[0059] As a non-limiting example, the polyester polyol may be preparedby reacting one or more polyepoxides with one or more polycarboxylicacids. Useful polyepoxides contain at least two epoxy groups with thediepoxides being most preferred. Among the preferred diepoxides usefulin the preparation of such a polyester polyol are diglycidyl ether ofbisphenol A and butyl diglycidyl ether. Useful polycarboxylic acids maybe selected from aliphatic, cycloaliphatic, and aromatic polycarboxylicacids and mixtures thereof, with those containing no ethylenicunsaturation and bearing no hydroxy functionality being most preferred.Exemplary of the many acids which may be employed are phthalic acid,isophthalic acid, terephthalic acid, oxallic acid, malonic acid,succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid,1,4-napthalenedicarboxylic acid, 2,3-napthalenedicarboxylic acid,2,6-napthalenedicarboxylic acid and the like. Additionally,monocarboxylic acids may be included such as benzoic acid, t-butylbenzoic acid and acetic acid.

[0060] It will be appreciated that various combinations of carboxylicacids and epoxides within the scope of the invention other than thosespecifically discussed above may be reacted in order to providepolyester polyols useful in the present one-component, waterbomefilm-forming composition. For example, oligoesters bearing hydroxyfunctionality other than that produced by the esterification reactionmay be produced by reacting not just a hydroxy bearing carboxylic acidwith an epoxide as discussed above, but by reacting carboxylic acids andepoxides, either of which bears hydroxy functionality.

[0061] The polyester polyol used in the present invention may be of anysuitable molecular weight. The molecular weight of the polyester polyolmay be at least 250, in some cases at least 500, in other cases at least1,000, in some instances at least 750 and in other instances at least1,000. Additionally, the molecular weight of the polyester polyol may beup to 25,000, in some cases up to 15,000, in other cases up to 10,000,in some instances up to 5,000 and in other instances up to 3,000 asdetermined by GPC using polystyrene standards. The molecular weight ofthe polyester polyol is selected based on the flow properties desired incomponent (A) and the properties desired in the coating film resultingfrom the present one-component, waterbome film-forming composition. Themolecular weight of the polyester polyol may be any value or any rangeof values inclusive of those stated above.

[0062] The polymer-polymer complex of component (A) may have a hydroxylequivalent weight of at least 200, in some cases at least 300, in othercases at least 400, in some instances at least 500 and in otherinstances at least 1,000 grams per equivalent. Additionally, thepolymer-polymer complex of component (A) may have a hydroxyl equivalentweight of not more than 5,000, in some cases not more than 4,000, inother cases not more than 3,500, in some instances not more than 3,000and in other instances not more than 2,000 grams per equivalent. Theterm “equivalent weight” is a calculated value based on the relativeamounts of the various ingredients used in making the specified materialand is based on the solids of the specified material. The relativeamounts are those that result in the theoretical weight in grams of thematerial, such as a polymer produced from the ingredients, and give atheoretical number of the particular functional group that is present inthe resulting polymer. The theoretical polymer weight is divided by thetheoretical number to give the equivalent weight. For example, hydroxylequivalent weight is based on the equivalents of reactive pendant and/orterminal hydroxyl groups in the hydroxyl-containing polymer.

[0063] As indicated above, in addition to (A), the presentone-component, waterborne film-forming composition further includes acrosslinking agent (B) having functional groups that are reactive withthe hydroxyl groups in (A). The crosslinking agents typically areblocked polyisocyanates and/or aminoplasts. By “blocked” or “capped”, ismeant is that the isocyanate groups have been reversibly reacted with acompound so that the resultant blocked isocyanate group is stable toactive hydrogens at ambient temperature but reactive with activehydrogens in the film-forming polymer at elevated temperatures, forexample, at temperatures between 30° C. and 200° C.

[0064] In an embodiment of the present invention, the blocked or cappedisocyanate of (B) includes a compound comprising a blocking group and apolyisocyanate compound. When a blocked or capped polyisocyanate isused, it may be blocked (or capped) using any suitable aliphatic,cycloaliphatic or aromatic alkyl monoalcohol phenol, or with anotheralcohol, or a beta diol known to those skilled in the art that can beused as a blocking agent for the polyisocyanate. Other suitable blockingagents include oximes and lactams. When used, the blocked polyisocyanatetypically is present, when added to the other components which form thethermosetting film-forming composition of the present invention, in anamount ranging from 5 to 65 weight percent, and can be present in anamount ranging from 10 to 45 weight percent, and often is present in anamount ranging from 15 to 40 percent by weight based on the total weightof resin solids present in the film-forming composition.

[0065] Other blocked isocyanate compounds that may be used in thepresent invention include the tricarbamoyl triazine compounds describedin detail in U.S. Pat. No. 5,084,541, which is incorporated by referenceherein. When used, such blocked isocyanates can be present, when addedto the thermosetting composition, in an amount ranging up to 20 weightpercent, and can be present in an amount ranging from 1 to 20 weightpercent, based on the total weight of resin solids present in thefilm-forming composition.

[0066] The polyisocyanates can be fully blocked as described in U.S.Pat. No. 3,984,299 column 1 lines 1 to 68, column 2 and column 3 lines 1to 15, or partially blocked and reacted with the polymer backbone asdescribed in U.S. Pat. No. 3,947,338 column 2 lines 65 to 68, column 3and column 4 lines 1 to 30, which are incorporated by reference herein.

[0067] Any suitable aliphatic, cycloaliphatic, or aromatic alkylmonoalcohol or phenolic compound may be used as a capping agent for thecapped polyisocyanate curing agent in the coating composition of thepresent invention including, for example, lower aliphatic alcohols suchas methanol, ethanol, and n-butanol; cycloaliphatic alcohols such ascyclohexanol; aromatic-alkyl alcohols such as phenyl carbinol andmethylphenyl carbinol; and phenolic compounds such as phenol itself andsubstituted phenols wherein the substituents do not affect coatingoperations, such as cresol and nitrophenol.

[0068] Glycol ethers may also be used as capping agents. Suitable glycolethers include ethylene glycol butyl ether, diethylene glycol butylether, ethylene glycol methyl ether and propylene glycol methyl ether.

[0069] Other suitable capping agents include oximes such as methyl ethylketoxime, acetone oxime and cyclohexanone oxime, lactams such asepsilon-caprolactam, and amines such as dibutyl amine.

[0070] In the present invention, the polyisocyanate of the blockedpolyisocyanate may be one or more suitable polyisocyanates. Suitablepolyisocyanates include, but are not limited to, 1,4-tetramethylenediisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate,4,4′-methylene-bis-(cyclohexyl isocyanate), p-phenylene diisocyanate,diphenylmethane-4,4′-diisocyanate, 2,4-toluene diisocyanate, 2,6-toluenediisocyanate, triphenylmethane-4,4′,4″-triisocyanate, 1,2,4-benzenetriisocyanate, polymethylene polyphenyl isocyanate, the isocyanurate ofhexamethylene diisocyanate, the biuret of hexamethylene diisocyanate,the isocyanurate of isophorone diisocyanatemeta-α,α,α′,α′-tetramethylxylylenediisocyanate, andpara-α,α,α′,α′-tetramethylxylylenediisocyanate.

[0071] When the blocking or capping agent is a lower aliphatic alcohol,nonlimiting examples include methanol, ethanol, and n-butanol. When theblocking or capping agent is a cycloaliphatic alcohol, a nonlimitingexample is cyclohexanol. When the blocking or capping agent is anaromatic-alkyl alcohol, nonlimiting examples include phenyl carbinol andmethylphenyl carbinol. When the blocking or capping agent is a phenoliccompound, non-limiting examples include phenol, substituted phenols,cresol and nitrophenol. When the blocking or capping agent is an oxime,non-limiting examples include methyl ethyl ketoxime, acetone oxime andcyclohexanone oxime. When the blocking or capping agent is a lactam, anon-limiting example is epsilon-caprolactam. A non-limiting example ofan amine blocking or capping agent is dibutyl amine.

[0072] Suitable aminoplasts for use as the crosslinking agent (B) mayinclude the condensation products obtained from the reaction of alcoholsand formaldehyde with one or more amines. In this embodiment, thecondensation products obtained from the reaction of alcohols andformaldehyde with melamine, urea or benzoguanamine is most commonlyused. While the aldehyde employed is most often formaldehyde, othersimilar condensation products can be made from other aldehydes, such asacetaldehyde, crotonaldehyde, acrolein, benzaldehyde, furfural, glyoxaland the like.

[0073] Condensation products of other amines and amides can also beused, for example, aldehyde condensates of triazines, diazines,triazoles, guanadines, guanamines and alkyl- and aryl-substitutedderivatives of such compounds, including alkyl- and aryl-substitutedureas and alkyl- and aryl-substituted melamines. Non-limiting examplesof such compounds include N,N′-dimethyl urea, benzourea, dicyandiamide,formaguanamine, acetoguanamine, glycoluril, ammeline,3,5-diaminotriazole, triaminopyrimidine,2-mercapto-4,6-diaminopyrimidine and carbamoyl triazines of the formulaC₃N₃(NHCOXR)₃ where X is nitrogen, oxygen or carbon and R is a loweralkyl group having from one to twelve carbon atoms or mixtures of loweralkyl groups, such as methyl, ethyl, propyl, butyl, n-octyl and2-ethylhexyl. Such compounds and their preparation are described indetail in U.S. Pat. No. 5,084,541, which is hereby incorporated byreference.

[0074] The aminoplast resins can contain methylol or similar alkylolgroups, and in most instances at least a portion of these alkylol groupsare etherified by reaction with an alcohol. Any monohydric alcohol canbe employed for this purpose, including methanol, ethanol, propanol,butanol, pentanol, hexanol or heptanol, as well as benzyl alcohol andother aromatic alcohols, cyclic alcohols such as cyclohexanol,monoethers of glycols, and halogen-substituted or other substitutedalcohols such as 3-chloropropanol and butoxyethanol.

[0075] In the present film-forming composition, (A) and (B) can react toeffect cure at suitable temperatures when the one-component, waterbornefilm-forming composition of the present invention is applied to asubstrate. The film-forming composition may cure at 60° C.; on the otherhand, it may cure at 70° C. or above; if required it may cure at 80° C.or above; in some cases it will be required to cure at 100° C. or aboveand in other situations at 100° C. or above. When the crosslinking agentof (B) is a blocked polyisocyanate, the cure temperature will typicallybe at least 100° C. Additionally, the film-forming composition may cureat up to 200° C.; on the other hand, it may cure at up to 190° C.; ifrequired it may cure at up to 180° C.; in some cases it will be requiredto cure at up to 170° C. and in other situations at up to 160° C. Thecure temperature of the film-forming composition may be any value or anyrange of values inclusive of those stated above.

[0076] Generally, component (A) is present in the film-formingcomposition of the present invention in an amount of at least 25 weightpercent, in some cases at least 30 weight percent, in other cases atleast 35 weight percent, in some instances at least 40 weight percentand in other instances at least 50 weight percent based on total resinsolids of the coating composition. Additionally, component (A) ispresent in the film-forming composition in an amount of up to 99 weightpercent, in some cases up to 95 weight percent, in other cases up to 90weight percent, in some instances up to 80 weight percent and in otherinstances up to 70 weight percent based on total resin solids of thecoating composition. The amount of component (A) is determined byvariables such as the properties desired in the final coated film andthe speed of cure. The amount of component (A) present in thefilm-forming composition may be any value or any range of valuesinclusive of those stated above.

[0077] Generally, component (B) is present in the film-formingcomposition of the present invention in an amount of at least 1 weightpercent, in some cases at least 5 weight percent, in other cases atleast 10 weight percent, in some instances at least 20 weight percentand in other instances at least 30 weight percent based on total resinsolids of the coating composition. Additionally, component (B) may bepresent in the film-forming composition in an amount of up to 75 weightpercent, in some cases up to 70 weight percent, in other cases up to 65weight percent, in some instances up to 60 weight percent and in otherinstances up to 50 weight percent based on total resin solids of thecoating composition. The amount of component (B) is determined byvariables such as the properties desired in the final film and the speedof cure. The amount of component (B) present in the film-formingcomposition may be any value or any range of values inclusive of thosestated above.

[0078] If desired, the present film-forming composition can compriseother optional materials well known in the art of formulated surfacecoatings, such as surfactants, flow control agents, thixotropic agentssuch as bentonite clay, fillers, organic cosolvents, catalysts,including phosphonic acids and other customary auxiliaries. Thesematerials can constitute up to 40 percent by weight of the total weightof the coating composition.

[0079] The solids content of the present film-forming composition may beat least 20 weight percent, in some cases at least 25 weight percent, inother cases at least 30 weight percent, in some instances at least 35weight percent and in other instances at least 40 weight percent basedon the total weight of the film-forming composition. Additionally, thesolids content of the present film-forming composition may be up to 75weight percent, in some cases up to 70 weight percent, in other cases upto 65 weight percent, in some instances up to 60 weight percent and inother instances up to 50 weight percent based on the total weight of thefilm-forming composition. The solids content of the film-formingcomposition may be any value or any range of values inclusive of thosestated above.

[0080] Any of the film-forming compositions previously described can beused advantageously to form a clear topcoat in a multi-componentcomposite coating composition, such as a color-plus-clear compositecoating. A color-plus-clear composite coating typically comprises a basecoat deposited from a pigmented or colored film-forming composition, anda transparent or clear topcoat applied over the base coat. A furtherembodiment of the present invention relates to such a multi-layercomposite coating. The multi-layer composite coating includes a basecoat layer deposited from a pigmented film-forming base coatcomposition; and a substantially pigment free topcoat deposited over atleast a portion of the base coat layer from a topcoat composition, wherethe topcoat composition comprises the present one-component, waterbomefilm-forming composition.

[0081] The multi-component composite coating of the present inventioncan be applied to various substrates to which they adhere, includingwood, metals, glass, cloth, polymeric substrates and the like. They areparticularly useful for coating metals and elastomeric substrates thatare found on motor vehicles. The compositions can be applied byconventional means including brushing, dipping, flow coating, sprayingand the like, but they are most often applied by spraying. The usualspray techniques and equipment for air spraying and electrostaticspraying and either manual or automatic methods can be used. Duringapplication of the coating composition to the substrate, ambientrelative humidity can range from about 30 to about 60 percent. Thecoating composition of the present invention is particularlyadvantageous when applied at an ambient relative humidity ranging fromabout 40 to about 60 percent, yielding very smooth finishes.

[0082] Another embodiment of the present invention is directed to acoated substrate that includes a substrate and the multi-layer compositecoating composition described above over at least a portion of thesubstrate. Any suitable substrate may be used. As non-limiting examples,suitable substrates can include a metallic substrate or an elastomericsubstrate.

[0083] When preparing the present multi-layer composite coating, a basecoat coating composition is first applied to the surface of thesubstrate to be coated to form a base coat layer thereon. The base coatcoating composition can be waterbome, solventborne or powdered, andtypically includes a film-forming resin, crosslinking material (such asare discussed above) and pigment. Non-limiting examples of suitable basecoat coating compositions include waterborne base coats forcolor-plus-clear composites such as are disclosed in U.S. Pat. Nos.4,403,003; 4,147,679; and 5,071,904, each of which is incorporated byreference herein.

[0084] After application of the base coating to the substrate, a film isformed on the surface of the substrate by driving water out of the filmby heating or by an air-drying period. Typically, the coating thicknessranges from about 0.1 to about 5 mils (about 2.54 to about 127 microns),and preferably about 0.4 to about 1.5 mils (about 10.16 to about 38.1microns) in thickness.

[0085] The heating will preferably be only for a short period of timeand will be sufficient to ensure that the topcoat can be applied to thebase coat if desired without the former dissolving the base coatcomposition. Suitable drying conditions will depend on the particularbase coat composition and on the ambient humidity, but in general adrying time of from about 1 to 5 minutes at a temperature of about80-250° F. (20-121° C.) will be adequate to ensure that mixing of thetwo coats is minimized. At the same time, the base coat film isadequately wetted by the topcoat composition so that satisfactoryintercoat adhesion is obtained. Also, more than one base coat andmultiple topcoats may be applied to develop the optimum appearance.Usually between coats, the previously applied coat is flashed; that is,exposed to ambient conditions for about 1 to 20 minutes.

[0086] After application of the base coat in a composition, a topcoatcan be formed by depositing any of the film-forming compositionsdescribed in detail above thereover. Preferably, the topcoat coatingcomposition is chemically different or contains different relativeamounts of ingredients from the base coat coating composition.

[0087] The film-forming (topcoat) coating composition can be applied tothe surface of the base coat by any of the coating processes discussedabove for applying the base coat coating composition to the substrate.The coated substrate may be heated to cure the coating layers. In thecuring operation, solvents are driven off and the film-forming materialsof the clearcoat and the base coat are each crosslinked. The heating orcuring operation may be carried out at 60° C. or above; on the otherhand, it may be carried out at 70° C. or above; if required it may becarried out at 80° C. or above; in some cases it will be required to becarried out at 100° C. or above and in other situations at 120° C. orabove. When the crosslinking agent is a blocked polyisocyanate, thecuring operation is typically carried out at a temperature of at least100° C. Additionally, the heating or curing operation of thefilm-forming materials of the clearcoat and the base coat may be carriedout at up to 200° C.; on the other hand, it may be carried out at up to190° C.; if required it may be carried out at up to 180° C.; in somecases it will be required to be carried out at up to 170° C. and inother situations at up to 160° C. The heating or curing operation may becarried out at any temperature or any range of temperatures inclusive ofthose stated above.

[0088] The thickness of the topcoat may be at least 0.25 mils (6.3microns), in some cases at least 0.5 mils (12.7 microns), in other casesat least 0.75 mils (19.1 microns), in some instances at least 1.0 mils(25.4 microns) and in other instances at least 1.25 mils (31.7 microns).Additionally, the thickness of the clearcoat may be up to 7 mils (177.8microns), in some cases up to 5 mils (127 microns), in other cases up to4 mils (101.6 microns), in some instances up to 3 mils (76.2 microns)and in other instances up to 2.5 mils (63.5 microns). The thickness ofthe topcoat may be any thickness or any range of thicknesses inclusiveof those stated above.

[0089] In certain embodiments of the present invention, the crosslinkdensity of the cured film-forming composition, i.e., the degree ofcrosslinking, ranges from 5% to 100% of complete crosslinking. In otherembodiments, the crosslink density ranges from 35% to 85% of fullcrosslinking. In other embodiments, the crosslink density ranges from50% to 85% of full crosslinking. One skilled in the art will understandthat the presence and degree of crosslinking, i.e., the crosslinkdensity, can be determined by a variety of methods, such as dynamicmechanical thermal analysis (DMTA) using a Polymer Laboratories MK IIDMTA analyzer conducted under nitrogen. This method determines the glasstransition temperature and crosslink density of free films of coatingsor polymers. These physical properties of a cured material are relatedto the structure of the crosslinked network.

[0090] According to this method, the length, width and thickness of asample to be analyzed are first measured, the sample is tightly mountedto the Polymer Laboratories MK III apparatus, and the dimensionalmeasurements are entered into the apparatus. A thermal scan is run at aheating rate of 3° C./min, a frequency of 1 Hz, a strain of 120%, and astatic force of 0.01N, and sample measurements occur every two seconds.The mode of deformation, glass transition temperature and crosslinkdensity of the sample can be determined according to this method. Highercrosslink density values indicate a higher degree of crosslinking in thecoating.

[0091] The one-component, waterbome film-forming composition of thepresent invention, when used as a coating composition, demonstratesexcellent gloss, film hardness, solvent and acid resistance whilecontaining minimal volatile organic solvents.

[0092] The present invention will further be described by reference tothe following examples. The following examples are merely illustrativeof the invention and are not intended to be limiting. Unless otherwiseindicated, all percentages are by weight.

EXAMPLE 1

[0093] The ingredients listed below were used to prepare a polyesterpolyol. Component Weight (grams) 1,4-Cyclohexane 344.0 Dicarboxylic AcidIsostearic Acid 568.0 Trimethylol propane 540.0 Triphenyl phosphite 3.6Dibutyltin Oxide 2.6

[0094] The components were charged into a three-liter, four-necked roundbottom flask equipped with a motor driven stainless steel paddleagitator, a thermocouple to record batch temperature, a Dean-Stark watertrap connected with a condenser to collect distillate evolved and anitrogen sparge tube.

[0095] The synthesis was performed using azeotropic conditions withxylene (3% on solids). Heat was applied to a Glas-Col heating mantle andthe temperature was gradually increased to about 220° C. and held untilan acid value of less than four, as measured by potentiometric titrationwith KOH, was obtained.

EXAMPLE 2

[0096] This example demonstrates the synthesis of the stable aqueousdispersion of a combination of a polyester polyol and a carboxylicacid-containing acrylic polymer polyol of the present invention. Thesynthesis used the ingredients shown below: Amount Resin SolidsIngredient (grams) (weight %) Charge 1 Glycidyl ester of brancheddecanoic acid¹ 961.9 29.5 Charge 2 di-t-amyl peroxide 62.7 m-styrenedimer 91.2 Charge 3 Butyl acrylate 326.5 10.0 Styrene 714.1 21.9Hydroxyethyl acrylate 668.2 20.5 2-ethylhexyl acrylate 231.0 7.07Acrylic acid 363.6 11.1 Charge 3A Polyester Polyol of Example 1 422.110.0 Charge 4 Dimethyl ethanol amine 120.0 Charge 5 Deionized water5538.7

[0097] Charge 1 was added to a reaction vessel equipped with a refluxcondenser and nitrogen blanket and heated to 160° C. Charge 3 and Charge3A were mixed together and the mixture was added to the reaction vesselover a four-hour period. Beginning at the same time as the mixture,charge 2 was added to the reaction vessel over a 4.5-hour period, afterwhich time the resulting product continued to be mixed in the vessel at160° C. The product was cooled to 100° C. and charge 4 was added over a30-minute period of time. Charge 5 was pre-heated to 70° C. and added tothe vessel over a 30-minute period. The product was mixed for one hourat 100° C. and decanted. The resulting product had total solids of 38.9weight percent (1 hour at 110° C.), pH of 8.4 and viscosity of 170 cps(Brookfield, RVT spindle #1, 30 rpm at 22.3° C.). The average particlesize of the dispersed particles was 0.08-0.09 μm determined by HoribaLA-900 Laser Scattering Particle Size Distribution Analyzer, availablefrom Horiba Instruments, Irvine, Calif.

[0098] The resulting latex did not demonstrate any visible sign ofseparation after standing for 4 months at ambient conditions.

EXAMPLE 3

[0099] This is a comparison example demonstrating the synthesis of anaqueous dispersion where a polyester polyol and a carboxylicacid-containing acrylic polymer polyol are physically mixed aftersynthesis of the acrylic polyol. An acrylic polyol was prepared usingthe ingredients shown below: Amount Resin Solids Ingredient (grams)(weight %) Charge 1 Glycidyl ester of branched decanoic acid¹ 961.9 29.5Charge 2 di-t-amyl peroxide 62.7 m-styrene dimer 91.2 Charge 3 Butylacrylate 326.5 10.0 Styrene 714.1 21.9 Hydroxyethyl acrylate 668.2 20.52-ethylhexyl acrylate 231.0 7.07 Acrylic acid 363.6 11.1 Charge 4Dimethyl ethanol amine 120.0 Charge 5 Deionized water 5538.7

[0100] Charge 1 was added to a reaction vessel equipped with a refluxcondenser and nitrogen blanket and heated to 160° C. Charge 3 was addedto the reaction vessel over a four-hour period. Beginning at the sametime as the mixture, charge 2 was added to the reaction vessel over a4.5-hour period, after which time the resulting product continued to bemixed in the vessel at 160° C. The product was cooled to 100° C. andcharge 4 was added over a 30-minute period of time. Charge 5 waspre-heated to 70° C. and added to the vessel over a 30-minute period.The product was mixed for one hour at 100° C. and decanted. The averageparticle size of the dispersed particles was 0.08-0.09 μm, determined byHoriba LA-900 Laser Scattering Particle Size Distribution Analyzer. Theresulting latex did not demonstrate any visible sign of separation afterstanding 4 months at ambient conditions.

[0101] The acrylic polyol described above was physically mixed with thepolyester polyol of example 1, at a solids ratio of 9:1 acrylic polyolto polyester polyol, using an overhead mixer for 20 minutes. The averageparticle size of the particles in the resulting dispersion was about 10μm, determined by Horiba LA-900 Laser Scattering Particle SizeDistribution Analyzer. The dispersion separated within a week into twolayers, demonstrating its instability compared to the dispersion of thepresent invention shown in Example 2.

EXAMPLES 4 AND 5

[0102] A waterbased clearcoat (for Example 4) was prepared from thefollowing ingredients: INGREDIENTS AMOUNTS (grams) Component I: Polymerof Example 2 71.5 Component II: Cymel 327² 8.72 DMP-Blocked HDI trimer³5.60 Tinuvin 1130⁴ 0.80 Tinuvin 292⁴ 0.50 Silicone surfactant⁵ 0.40Silicone oil⁶ 0.02 High boiling alcohol⁷ 2.00 Component III: Deionizedwater 10.46

[0103] Waterbased clearcoat compositions were prepared from thecomponents indicated above. Charge II was mixed separately underagitation for 1 hour at room temperature. Charge II was added intocharge I under agitation for 15 minutes and kept stirring for anadditional 1 hour. The dispersion was then allowed to sit overnight.Charge III was added slowly under agitation to bring the dispersion tothe spraying viscosity of 30 seconds efflux cup DIN 4 23° C.

[0104] Application:

[0105] The waterborne clearcoat described above (Example 4) and acommercial waterborne clearcoat, HYDROKLARLACK PPG 97020 available fromPPG Industries, Inc., Pittsburgh, Pa. (Example 5), were applied in ahumidity and temperature controlled spray booth at 60% relative humidity(“RH”) and 70° F. (21° C.) onto cold rolled steel substrates which hadbeen previously electrocoated with ED5000 and primed with 1177225A grayprimer (both products available commercially from PPG Industries, Inc.),the primed panels having been prepared by ACT Laboratories Inc., ofHillsdale Mich. Each of the waterborne clearcoat formulations wasspray-applied using the SATA LP90 gun with a MSB nozzle and 135 air cap.The coatings were applied over a commercial silver metallic waterbomebasecoat available from PPG Industries, Inc. The basecoat was applied intwo coats, with 60 second flash between coats and then prebaked for 10minutes at 176° F. (80° C.). The clearcoat was then applied in two coatswithout any flash. The clearcoated panels were allowed to flash for fiveto ten minutes at ambient condition and baked for 10 minutes at 140° F.(60° C.) and finally, for 30 minutes at 293-302° F. (145-150° C.).Panels were baked in a horizontal position. The film build wasapproximately 2.0 mils.

[0106] Delamination Test:

[0107] Demineralized water was dripped onto test panels at 63° C. for 72hours. The test panels were then taken off of the water drip and driedwith a clean cloth. Subsequently the surface was scratched using aCross-Cut Tester (Byk-Chemie, Wesel, Germany) by cutting through thefilm to the substrate in one steady motion. A second cut was made,perpendicular to and centered on the first cut. Next, a lap of tape(Scotch Brand 800, 3M, St. Paul, Minn.) was placed and rubbed firmlyover the cut. The tape was removed in a rapid upward motion. The tapeand removal step was then repeated. Separation of the coating from thesubstrate should be no more than 1 mm along the scratch with noseparation of the coating on the remaining area.

[0108] Acid Test 1:

[0109] A Gradient oven from Byk Gardner was used at a temperature rangeof 41-81° C. Several drops (each with a volume of 250 μl of a solutionof 10% by weight sulfuric acid were applied to a preheated test panel atdistance corresponding to the heating elements. Application of the acidsolution was completed within 60 seconds, after which temperaturestressing of the test panel for a period of 30 minutes was begun. Thetest panel was then removed from the gradient oven, then rinsed indeionized water and dried under a cold air stream. The evaluation wasperformed visually. The temperature at which the test panel showed thefirst signs of damage was recorded. The temperature at which the firstvisible signs of damage occur should be greater than 60° C. after 30minutes of storage time. Acid test 2:

[0110] Several drops of 38% by weight sulfuric acid are applied to atest panel. No visible signs of damage should be seen before 72 hours atroom temperature.

[0111] 20° Gloss:

[0112] Specular gloss was measured at 20° with a Novo Gloss StatisticalGlossmeter (Paul N. Gardner Company, Inc., Pompano Beach, Fla.) wherehigher numbers indicate better performance.

[0113] Hardness:

[0114] Hardness was measured using the Tukon Microhardness InstrumentModel 300 (Wilson Instruments Division of Instron Corporation, Canton,Mass.). Higher numbers indicate better performance.

[0115] Results from the evaluations of the coated panels baked at 140°C. (285° F.) for gloss, indentation hardness, delamination, humidityresistance, adhesion and acid resistance are summarized in the tablebelow. Example 5 Example 4 (Comparative) Gloss 20° 96.3 91.5 Hardness71   77   Acid resistance Pass Pass Test 1 Pass Pass Test 2 Delaminationtest Pass Pass

[0116] Example 4 included 13% solvent, while the conventional coating ofComparative Example 5 included 40% by weight solvent. These data showthat the film-forming composition of the present invention (Example 4)provided better gloss than that of Comparative Example 5 made using acommercially available polymer, and in other respects provided acomparable coating, while containing significantly less volatilesolvent.

[0117] Those skilled in the art will recognize that changes may be madeto the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications that are within the spirit and scopeof the invention, as defined by the appended claims.

We claim:
 1. A one-component, waterbome film-forming compositioncomprising: (A) a stable aqueous dispersion of a mixture of a polyesterpolyol and a carboxylic acid-containing acrylic polymer polyol, whereinthe weight ratio of polyester polyol to acrylic polymer polyol is in therange of 10:90 to 30:70; and (B) a crosslinking agent having functionalgroups reactive with the hydroxyl groups in (A) selected from the groupof blocked isocyanates and aminoplasts.
 2. The film-forming compositionof claim 1, wherein the crosslinking agent in (B) is a blockedpolyisocyanate and the equivalent ratio of hydroxyl groups in (A) toisocyanate functional groups in (B) is from 0.8:1 to 1.7:1.
 3. Thefilm-forming composition of claim 1, wherein the crosslinking agent in(B) is an aminoplast and the aminoplast is present at from 10 to 60percent by weight of the total resin solids of the film-formingcomposition.
 4. The film-forming composition of claim 1, whereincomponent (A) is prepared by polymerizing a mixture of ethylenicallyunsaturated polymerizable monomers comprsing: (1) at least onecarboxylic acid group-containing monomer; (2) at least one primaryalcohol group-containing monomer; (3) at least one glycidyl ester of analiphatic saturated monocarboxylic acid; and (4) at least one polyesterpolyol.
 5. The film-forming composition of claim 1, wherein thepolyester polyol and the carboxylic acid-containing acrylic polymerpolyol in (A) are present as a stable polymer-polymer complex.
 6. Thefilm-forming composition of claim 2, wherein after polymerization iscomplete, an amine is added to component (A) in an amount sufficient toprovide a pH of from 7 to 10 when component (A) is dispersed in water.7. The film-forming composition of claim 6, wherein the pH is increasedby using one or more volatile amines.
 8. The film-forming composition ofclaim 7, wherein the amines are selected from the group consisting ofdimethylethanolamine, ammonia, triethyl amine and diethyl propanolamine.
 9. The film forming composition of claim 4, wherein theequivalent ratio of the carboxylic acid groups from the carboxylic acidgroup-containing monomer to the epoxy group of the glycidyl ester of analiphatic saturated monocarboxylic acid is greater than 1:1.
 10. Thefilm-forming composition of claim 4, wherein the polymerizationcomprises the steps of: (a) introducing components (1) and (2) to asuitable reactor; and (b) adding components (3) and (4) to the reactor,along with a suitable free radical polymerization initiator, in thesubstantial absence of a solvent.
 11. The film-forming resin of claim 4,wherein the glycidyl ester (3) is a glycidyl ester having the followingstructure:

wherein R¹ is C₁-C₁₈ linear or branched alkyl and R² and R³ areindependently selected from H and C₁-C₁₈ linear or branched alkyls. 12.The film-forming resin composition of claim 4, wherein the carboxylicacid group-containing monomer (1) is one or more selected from the groupconsisting of acrylic acid and (meth)acrylic acid and the monomercontaining a primary alcohol group is one or more selected from thegroup consisting of hydroxyethylacrylate, hydroxyethyhnethacrylate,hydroxypropylacrylate, hydroxypropylmethacrylate and hydroxybutyl(meth)acrylate.
 13. The film-forming composition of claim 1, wherein (A)and (B) are curable at a temperature of from 60° C. to 140° C.
 14. Thefilm-forming composition of claim 1, wherein the blocked isocyanate of(B) comprises a compound comprising a blocking group and apolyisocyanate compound.
 15. The film-forming composition of claim 14,wherein the polyisocyanate is at least one selected from the groupconsisting of 1,4-tetramethylene diisocyanate, 1,6-hexamethylenediisocyanate, isophorone diisocyanate, 4,4′-methylene-bis-(cyclohexylisocyanate), p-phenylene diisocyanate,diphenylmethane-4,4′-diisocyanate, 2,4-toluene diisocyanate, 2,6-toluenediisocyanate, triphenylmethane-4,4′,4″-triisocyanate, 1,2,4-benzenetriisocyanate, polymethylene polyphenyl isocyanate, the isocyanurate ofhexamethylene diisocyanate, the biuret of hexamethylene diisocyanate,the isocyanurate of isophorone diisocyanatemeta-α,α,α′,α′-tetramethylxylylenediisocyanate, andpara-α,α,α′,α′-tetramethylxylylenediisocyanate.
 16. The film-formingcomposition of claim 14, wherein the compound comprising a blockinggroup is at least one selected from the group consisting of aromaticalkyl monoalcohols, phenolic compounds, lower aliphatic alcohols,cycloaliphatic alcohols, aromatic-alkyl alcohols; glycol ethers, amines,lactams and oximes.
 17. The film-forming composition of claim 16,wherein the lower aliphatic alcohols are selected from the groupconsisting of methanol, ethanol, and n-butanol; the cycloaliphaticalcohols is cyclohexanol; the aromatic-alkyl alcohols are selected fromthe group consisting of phenyl carbinol and methylphenyl carbinol; thephenolic compounds are selected from the group consisting of phenol,substituted phenols, cresol and nitrophenol; the glycol ethers areselected from the group consisting of ethylene glycol butyl ether,diethylene glycol butyl ether, ethylene glycol methyl ether andpropylene glycol methyl ether; the oximes are selected from the groupconsisting of methyl ethyl ketoxime, acetone oxime and cyclohexanoneoxime, the lactam is epsilon-caprolactam, and the amine is dibutylamine.
 18. The film-forming composition of claim 1, wherein theaminoplast of (B) comprises the condensation products obtained from thereaction of alcohols and formaldehyde with one or more amines.
 19. Thefilm-forming composition of claim 18, wherein the amines are one or moreselected from the group consisting of melamine, urea, benzoguanamine,triazines, diazines, triazoles, guanadines and guanamines.
 20. Thefilm-forming composition of claim 18, wherein the alcohols are at leastone selected from the group consisting of aromatic alkyl monoalcohols,phenolic compounds, lower aliphatic alcohols, cycloaliphatic alcohols,aromatic-alkyl alcohols and glycol ethers.
 21. The film-forming resin ofclaim 4, wherein the mixture of monomers further comprises (5) acrosslinking monomer.
 22. A multi-layer composite coating comprising:(I) a base coat layer deposited from a pigmented film-forming base coatcomposition; and (II) a substantially pigment-free topcoat depositedover at least a portion of said base coat layer from a topcoatcomposition, wherein said topcoat composition is a one-component,waterbome film-forming composition comprising: (A) a stable aqueousdispersion of a mixture of a polyester polyol and a carboxylicacid-containing acrylic polymer polyol, wherein the weight ratio ofpolyester polyol to acrylic polymer polyol is in the range of 10:90 to30:70; and (B) a crosslinking agent having functional groups reactivewith the hydroxyl groups in (A) selected from the group of blockedisocyanates and aminoplasts.
 23. The multi-layer composite coating ofclaim 22, wherein the crosslinking agent in (B) is a blockedpolyisocyanate and the equivalent ratio of hydroxyl groups in (A) toisocyanate functional groups in (B) is from 0.8:1 to 1.7:1.
 24. Themulti-layer composite coating of claim 22, wherein the crosslinkingagent in (B) is an aminoplast and the aminoplast is present at from 10to 60 percent by weight of the total resin solids of the film-formingcomposition.
 25. The multi-layer composite coating of claim 22, whereinthe first component (A) is prepared by polymerizing a mixture ofethylenically unsaturated polymerizable monomers comprising: (1) atleast one carboxylic acid group-containing monomer; (2) at least oneprimary alcohol group-containing monomer; (3) at least one glycidylester of an aliphatic saturated monocarboxylic acid; and (4) at leastone polyester polyol.
 26. The multi-layer composite coating of claim 25,wherein the polyester polyol and the carboxylic acid-containing acrylicpolymer polyol in (A) are present as a stable polymer-polymer complex.27. The multi-layer composite coating of claim 25, wherein afterpolymerization is complete, an amine is added to component (A) in anamount sufficient to provide a pH of from 7 to 10 when component (A) isdispersed in water.
 28. The multi-layer composite coating of claim 27,wherein the pH is increased by using one or more volatile amines. 29.The multi-layer composite coating of claim 28, wherein the amines areselected from the group consisting of dimethylethanolamine, ammonia,triethyl amine and diethyl propanol amine.
 30. The multi-layer compositecoating of claim 25, wherein the equivalent ratio of the carboxylic acidgroups from the carboxylic acid group-containing monomer to the epoxygroup of the glycidyl ester of an aliphatic saturated monocarboxylicacid is greater than 1:1.
 31. The multi-layer composite coating of claim25, wherein the polymerization comprises the steps of: (a) introducingcomponents (1) and (2) to a suitable reactor; and (b) adding components(3) and (4) to the reactor, along with a suitable free radicalpolymerization initiator, in the substantial absence of a solvent. 32.The multi-layer composite coating of claim 25, wherein the glycidylester (3) is a glycidyl ester having the following structure:

wherein R¹ is C₁-C₁₈ linear or branched alkyl and R² and R³ areindependently selected from H and C₁-C₁₈ linear or branched alkyls. 33.The multi-layer composite coating of claim 25, wherein the carboxylicacid group-containing monomer (1) is one or more selected from the groupconsisting of acrylic acid and (meth)acrylic acid and the monomercontaining a primary alcohol group is one or more selected from thegroup consisting of hydroxyethylacrylate, hydroxyethylmethacrylate,hydroxypropylacrylate, hydroxypropylmethacrylate and hydroxybutyl(meth)acrylate.
 34. The multi-layer composite coating of claim 25,wherein (A) and (B) are curable at a temperature of from 60° C. to 200°C.
 35. The multi-layer composite coating of claim 25, wherein theblocked isocyanate of (B) comprises a compound comprising a blockinggroup and a polyisocyanate compound.
 36. The multi-layer compositecoating of claim 35, wherein the polyisocyanate is at least one selectedfrom the group consisting of 1,4-tetramethylene diisocyanate,1,6-hexamethylene diisocyanate, isophorone diisocyanate,4,4′-methylene-bis-(cyclohexyl isocyanate), p-phenylene diisocyanate,diphenylmethane-4,4′-diisocyanate, 2,4-toluene diisocyanate, 2,6-toluenediisocyanate, triphenylmethane-4,4′,4″-triisocyanate, 1,2,4-benzenetriisocyanate, polymethylene polyphenyl isocyanate, the isocyanurate ofhexamethylene diisocyanate, the biuret of hexamethylene diisocyanate,the isocyanurate of isophorone diisocyanatemeta-α,α,α′,α′-tetramethylxylylenediisocyanate andpara-α,α,α′,α′-tetramethylxylylenediisocyanate.
 37. The multi-layercomposite coating of claim 35, wherein the compound comprising ablocking group is at least one selected from the group consisting ofaromatic alkyl monoalcohols, phenolic compounds, lower aliphaticalcohols, cycloaliphatic alcohols, aromatic-alkyl alcohols, glycolethers, amines, lactams and oximes.
 38. The multi-layer compositecoating of claim 37, wherein the lower aliphatic alcohols are selectedfrom the group consisting of methanol, ethanol, and n-butanol; thecycloaliphatic alcohols is cyclohexanol; the aromatic-alkyl alcohols areselected from the group consisting of phenyl carbinol and methylphenylcarbinol; the phenolic compounds are selected from the group consistingof phenol, substituted phenols, cresol and nitrophenol; the glycolethers are selected from the group consisting of ethylene glycol butylether, diethylene glycol butyl ether, ethylene glycol methyl ether andpropylene glycol methyl ether; the oximes are selected from the groupconsisting of methyl ethyl ketoxime, acetone oxime and cyclohexanoneoxime; the lactam is epsilon-caprolactam and the amine is dibutyl amine.39. The multi-layer composite of claim 35, wherein the aminoplast of (B)comprises the condensation products obtained from the reaction ofalcohols and formaldehyde with one or more amines.
 40. The multi-layercomposite of claim 39, wherein the amines are one or more selected fromthe group consisting of melamine, urea, benzoguanamine, triazines,diazines, triazoles, guanadines and guanamines.
 41. The multi-layercomposite of claim 39, wherein the alcohols are at least one selectedfrom the group consisting of aromatic alkyl monoalcohols, phenoliccompounds, lower aliphatic alcohols, cycloaliphatic alcohols,aromatic-alkyl alcohols and glycol ethers.
 42. The multi-layer compositecoating of claim 22, wherein the mixture of monomers further comprises(5) a crosslinking monomer.
 43. A coated substrate comprising: (A) asubstrate, and (B) the multi-layer composite coating of claim 22 over atleast a portion of the substrate.
 44. The coated substrate of claim 43,wherein the substrate is selected from a metallic substrate and anelastomeric substrate.
 45. A coated substrate comprising: (A) asubstrate, and (B) the one-component, waterbome film-forming compositionof claim 1 over at least a portion of the substrate.
 46. The coatedsubstrate of claim 45, wherein the substrate is selected from a metallicsubstrate and an elastomeric substrate.